The present invention relates to a transducer mounting assembly for use in conjunction with an apparatus for determining the percentage of solid particles in a suspension ("consistency") and in particular to a transducer mounting assembly having a hinged collar adapted to be secured around a section of pipe having a suspension such as paper pulp stock flowing therethrough.
In paper manufacturing processes, the consistency of the pulp stock is a prime factor. For purposes of this disclosure the term "stock" is intended to mean wet pulp of any type at any stage in the paper manufacturing process. Different grades and weights of paper or paper products require different consistencies of stock. In addition, the consistency of pulp for a given paper product will depend on the process point at which a pulp sample is taken. The stock consists of the comminuted wood fibers, water, and sometimes certain additives. Such pulp stock is not a homogeneous mass, but rather is a mixture which contains the foregoing materials.
Since the consistency of the stock is of prime importance in the manufacturing of paper and paper products, it is highly desirable to know its consistency at all times. Further, in order to provide a reliable and high quality paper manufacturing operation, the consistency of unknown stock must be easily ascertained. Such a determination of consistency is particularly important when it is desired to switch a paper manufacturing apparatus from one grade of product to another. Such a grade change may necessitate the employment of stock having a different consistency.
The term "consistency" as used by the paper industry designates the concentration of pulp in water on a moisture-free basis. Consistency is expressed in terms of a percentage, with the percent consistency being calculated as follows: ##EQU1## In the pulp and paper industry, the consistency of stock may vary by three orders of magnitude, for example from 0.02% to 20%.
An apparatus and method for determining pulp stock consistency are disclosed in my co-pending U.S. Pat. No. 4,507,556 filed Dec. 8, 1982, which is incorporated herein by reference. A source of diffused radiant energy is provided which energy is directed toward a suspension to be measured. The portion of the energy which is forward-scattered by the suspension is detected and a first signal indicative of the magnitude of the forward-scattered energy is produced. The portion of energy which is back-scattered by the suspension is detected and a second signal indicative of the magnitude of back-scattered energy is produced. The first and second signals are combined at a predetermined ratio to produce a feedback signal used to control the intensity of energy emitted from the radiant energy source. The intensity of energy emitted from the source is a function of the forward-scattered and back-scattered energy and is directly proportional to the consistency of the suspension being measured. By monitoring the power driving the radiant energy source, a display calibrated in terms of percent consistency can be provided.
It is desirable to have a means for determining pulp stock consistency on a real-time basis during paper manufacture. facture. In order to accomplish this objective, means must be provided for monitoring the pulp stock as it flows through a process pipe. One way to accomplish this is disclosed in U.S. Pat. No. 4,040,743, wherein back-scattered, reflected, and transmitted energy is utilized to measure pulp slurry parameters. In this patent, an optical probe is provided within a molded housing which secures optics, windows and prisms in place and contains shoulders and an arcuate surface. The shoulders engage the outer surface of a pipe wall with a gasket disposed therebetween. An extension of the molded housing frictionally engages the walls of an aperture formed in the pipe wall. The probe assembly is secured in place by a strap. The arcuate surface of the molded housing and the windows lie in the plane described by the inner surface of the pipe wall. In order to use this structure, the pipe through which pulp stock is flowing must be cut open to provide the required aperture into which the molded probe housing fits. This results in a possibility of leakage and contamination of the pulp stock.
Various other patents disclose means for mounting radiation emitters and/or detectors around pipes or other cylindrical objects. For example, U.S. Pat. No. 2,759,175 relates to a leak detector for a pipe joint which uses a clamping arrangement for a thin, electrically conductive metal foil which surrounds the pipe joint. U.S. Pat. Nos. 2,967,938; 3,673,407; 3,519,824; and 3,445,655 all relate to various inspection means using some type of radiation emitter and detector in conjunction with a clamp for positioning the emitter and detector around a cylinder.
U.S. Pat. No. 4,022,245 discloses the use of a transparent sleeve around a check valve for visual inspection of the valve. The transparent window is not, however, used in conjunction with a radiation emitter and sensor arrangement which monitors parameters of a material flowing through a pipe.
clamping arrangements are shown in U.S. Pat. Nos. 1,893,702 and 3,664,621. Such arrangements do not relate to the mounting of radiation sources and detectors around a pipe for in-process measurement of desired parameters.
It would be advantageous to provide a transducer mounting assembly for use in conjunction with an apparatus for measuring the percentage of solid particles in a suspension flowing through a pipe. Such an assembly should provide for simple mounting to a pipe and subsequent removal from the pipe, and should not require any projection into an opening in the pipe which could result in leakage of a fluid from the pipe. The present invention relates to such a transducer mounting assembly.